1. Field of the Invention
The present invention relates to an electron source comprising plural electron emitting devices arranged in a predetermined shape, and a method of manufacturing the electron source. The present invention also relates to an image forming apparatus such as a display device comprising the electron source, and a method of manufacturing the image forming apparatus.
2. Description of the Related Art
Conventional electron emitting devices are roughly divided into two types, including thermionic electron-emitting devices, and cold-cathode electron emitting devices. Examples of cold-cathode electron emitting devices include a field emission type, a metal/insulator/metal type (MIM type), a surface conduction type, and the like.
The construction and manufacturing method of the surface conduction type of electron emitting devices are disclosed in, for example, Japanese Patent Laid-Open No. 8-321254.
FIGS. 65A and 65B schematically show the general construction of a conventional surface conduction type electron emitting device disclosed in the above publication. FIGS. 65A and 65B are respectively a plan view and a sectional view of the electron emitting device disclosed in the above publication.
In FIGS. 65A and 65B, reference numeral 1 denotes a base (substrate), reference numerals 2 and 3 denote a pair of opposed electrodes (device electrodes), reference numeral 4 denotes a conductive film, reference numeral 5 denotes a second gap, reference numeral 6 denotes a carbon film, and reference numeral 7 denotes a first gap.
FIG. 66, consisting of FIGS. 66A to 66D, schematically shows an example of a process for forming an electron emitting device having the structure shown in FIGS. 65A and 65B.
First, the pair of electrodes 2 and 3 is formed on the substrate 1 (FIG. 66A). Then, the conductive film 4 is formed for connecting the electrodes 2 and 3 (FIG. 66B). Then, in a “forming step” (“Forming”), a current is passed between the electrodes 2 and 3 to form the second gap 5 in the conductive film 4 (FIG. 66C). Furthermore, in an “activation step”, a voltage is applied across the electrodes 2 and 3 in a carbon compound atmosphere to form the carbon film 6 within the gap 5 on the substrate 1 to partially overlap with the conductive film 4 near the gap 5, to form the electron emitting device (FIG. 66D).
On the other hand, Japanese Patent Laid-Open No. 9-237571 discloses a method of manufacturing a surface conduction type of electron emitting device. Instead of the “activation step”, the method comprises a step of coating an organic material such as a thermosetting resin, an electron beam negative resist, polyacrylonitrile, or the like on a conductive film, and a step of carbonizing the coating.
An electron source comprising a plurality of the electron emitting devices manufactured by the above-described manufacturing method can be combined with an image forming member such as a fluorescent material or the like to obtain an image forming apparatus such as a flat display panel or the like.
In addition to the “forming step”, the “activation step” may be performed for the above-described conventional electron emitting device to form the carbon film 6 comprising carbon or a carbon compound, and having the narrower first gap 7 within the second gap 5 formed in the “forming step”, in order to obtain good electron emission properties.